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Most Planets In the Universe Are Homeless
StartsWithABang writes: We like to think of our Solar System as typical: a central star with a number of planets — some gas giants and some rocky worlds — in orbit around it. Yes, there's some variety, with binary or trinary star systems and huge variance in the masses of the central star being common ones, but from a planetary point of view, our Solar System is a rarity. Even though there are hundreds of billions of stars in our galaxy for planets to orbit, there are most likely around a quadrillion planets in our galaxy, total, with only a few trillion of them orbiting stars at most. Now that we've finally detected the first of these, we have an excellent idea that this picture is the correct one: most planets in the Universe are homeless. Now, thank your lucky star!"
don't planets need some kind of gravity source to pull all the dust and shit together?
so much resources out there for the taking, no need to come to earth
Planet is Greek for wanderer. So, I think the name is even more appropriate.
I always wondered why wandering planets couldn't be used instead of dark matter to explain where all the missing mass is.
This impacts Drake equation and might shed light as to why we have not detected any other sentient life in the universe.
No, it does not impact the Drake equation at all. The drake equation is based on R* and f(p) which are the the "rate of star formation" and the "fraction of those stars that have planets" (from your link on wikipedia). Both of these numbers are not affected by this finding.
Now not only do I have to be thankful that I have a roof over my head, now I have to be thankful I have a star over it to.
No it doesn't. This is just saying that most planets don't have solar systems, which in no way indicates that most solar systems don't have planets. The numbers given here put the ratio of planets to stars in the neighborhood of 10,000 to 1, so even if 0.1% of planets have homes within a solar system, that means an average solar system has about 10 planets.
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Actually these are not planets according to the new classification.
First, it must orbit the Sun.
Second, it must be big enough for gravity to squash it into a round ball.
And third, it must have cleared other objects out of the way in its orbital neighborhood.
http://missionscience.nasa.gov...
Space 1999 was so prescient!
2) These should be called slacker stars. They had so much potential, but just blew it all and eventually their parent's kicked them out.
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I wonder if the basic formation of a planetary system can occur without the center mass becoming large enough to be a star. Could you have a system of only unlit planets orbiting around each other. If the gas and dust is swirling around and clumping together, it could conceivably do that even though the mass at the center never gets big enough to ignite. Perhaps something about the way the center star is supposed to push the lighter elements out further away would cause something to not work out right, but to me it seems like it should still work in a similar fashion.
-- ssoorrrryy,, dduupplleexx sswwiittcchh oonn.. -Quote found on actual fortune cookie.
As I understand it, getting "captured in a gravity well" is actually pretty tricky. Unless you form in orbit around a larger body, you're most likely by far to just do a hyperbolic single-pass encounter. To be captured, you need to impact the larger body (a very rare occurrence), or dissipate your momentum in its atmosphere (almost as rare), or have some sort of multi-body interaction (probably rarer still).
This is all approximate -- technically, I guess everything orbits everything within its historical light-cone. Almost none of those orbits are anything close to periodic, though.
(FYI)
There are a few reasons astrophysicists know that it is extremely unlikely that dark matter is baryonic. First of all if all the stars in a galaxy shine on an object it heats up, this heat causes the release of radiation, called thermal radiation, and every (baryonic) object above zero kelvin (or -273.14 deg celcius) emits this radiation. However, dark matter does not emit any radiation at all (hence the name dark!)
If dark matter were baryonic it would also mean that it could become light emitting. If we got a clump of baryonic matter* and put it in space it would gravitationally contract, and would eventually form a star or black hole** - both of which we would be able to see.
So, because of these reasons the dark matter in galaxies and in galaxy groups/clusters cannot be baryonic, and so cannot be planets, dead stars, asteroids, etc. It would definetely not be planets as there is no way 10-100 times the mass of the stars in a galaxy would be planets, as the mechanism for making planets relies on supernovae, and the number of supernovae needed for the that many planets would be far too high to match our observations. I hope that this answered your question!
*provided the clump of baryonic matter was large, and the amount there is in galaxies definitely is!
** we don't observe black holes directly, but can see radiation from their accretion disks.
I thought orbiting a star was one of the criteria for an object to be called a planet.
We're out in the backwater. All the action is happening in the core.
Dark matter accounts for something like 90% of the gravitational effects that we see.
I've always suspected that "dark matter" very likely isn't matter at all. I suspect it is simply a gap in our model similar to how relativity filled in gaps for Newtonian mechanics. Dark matter (and dark energy) are basically placeholders for observations that do not match our model. That means one of two things. Either there is something we haven't observed yet OR there is something missing from our model. Both are quite possible but we seem fixated on that former when it could very easily be the later.
I actually do have some background in physics (college minor and worked in some research labs) and I've never have any "real" physicist give me a satisfactory explanation as to why invoking some mysterious matter/energy is a more likely answer than a gap in our models. We understand gravity probably the least of the four forces and we don't have a model that integrates it into our Standard Model. Seems to me that the place to look may very well be in the math rather than in the stars.
We've seen that with Jupiter, if it were not for being in orbit around Sol, Jupiter and its moons would effectively be their own dark solar system.
Homeless planets probably do fit to origin theories: 1.) Ejects and 2.) Self-formed.
Ejects would have a better chance at being smaller and denser because of the dust and debris field in the vicinity of the proto-star.
The self-formed more than likely are giants.
It little behooves the best of us to comment on the rest of us.
Systems composed of multiple stars (binaries, etc.) are more common than singular stars, like our Sun. A binary system is a risky place to be -- there is a strong probability that the gravitational interaction between the paired stars would, given enough time, eject any planetary body which forms there -- the "stable" regions depend on the orbital parameters of the two (or more) stars and can be limited to very narrow bands. So, if planetary formation is a typical process around stars and binaries are more common, then it's likely that the galaxy has a large population of planets ejected from unstable orbits around binaries.
For what it's worth, conjecture is that the Sun formed in a cluster and was, itself, ejected. Nearby stars with identical spectra (implying they formed from the same source material) have been identified.
Most really advance races will have probably passed through their singularity – being mechanical-beings they won't really need stars providing warmth to live by. It could be that a huge percentage of these planets are colonized by post-biological-entities and the planets around stars are left as garden areas for new post-biological-entities to emerge from.
Perhaps this is a new direction for SETI
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Gas giants could have moons that receive heat from gravitational changes and radiation from the gas giant. These moons might have life on them. It's an outside chance, yes, but given how many planets there are out there, I'd say the chances of one of these being in this situation is probably high.
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It's true, just saw one on the corner. Had a cardboard sign, "Will orbit for $$$".
I eat only the real part of complex carbohydrates.
If you're going to copy an answer from a post on another website, at least give the link:
http://astronomy.stackexchange...
And that answer obviously is wrong. If matter has clumped together into planets, it obviously hasn't clumped together into stars or black holes, and instead has clumped together into objects that are very hard to detect.
Arguments against dark matter being rogue planets are generally based on lack of enough microlensing observations and expected size distributions. But those are far from definitive.
So, the answer is: it is possible that dark matter is all rogue planets, although most physicists believe that it is not.
How can they claim that there's more of these homeless planets than not when they've only found one of them...ever!
I understand that we don't have to see something for it to be there but, this leap is just too big to bear.
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Don't mod this guy down. He's at least going by the definition from wikipedia (or a similar reference material), which states:A planet (from Ancient Greek (astr plants), meaning "wandering star") is an astronomical object orbiting a star or stellar remnant that (1) is massive enough to be rounded by its own gravity, (2) is not massive enough to cause thermonuclear fusion, and (3) has cleared its neighbouring region of planetesimals.
I'm sure what this article is calling a Planet meets these 3 criteria but do not meet the "circling a star or stellar remnant" apparent pre-requisite. What I cannot tell you is whether or not Wikipedia is wrong about that "needing to orbit a star" bit - I'm sure someone will respond with a reference defending or refuting that point.
A lot of physicists, including Neil deGrasse Tyson, have said that "Dark Matter" is actually a pretty poor name for the phenomenon because it's almost certainly not just some exotic form of matter
No clue who this Tyson guy is but either he, or you, have confused Dark Energy with Dark Matter. Physics is not determined by majority vote but I very strongly suspect that the numbers will come down massively in favour of Dark Matter being an exotic form of matter by which I mean some as yet undiscovered particle. Dark Matter is a very appropriate name for it since it almost certainly is matter and, lacking any electrical charge, will not interact with light at any wavelength. Attempts to explain Dark Matter by modifying newtonian mechanics are vastly more complicated and fine tuned than just adding an as yet unknown particle ever since the Bullet Cluster (and others like it) were discovered. While that is not proof that these models are wrong they fail Occam's Razor and, in general, solutions which fail this test turn out to be wrong which is why it is often used in science to select promising avenues for study.
Dark Energy on the other hand is definitely not a form of matter, for a start it is gravitationally repulsive, and is completely unknown. It is effectively Einstein's cosmological constant but when you use existing physics to try to predict this you end up with a constant 120 orders of magnitude (yes you read that correctly: 10^120) too large so it is safe to say that we are missing something here, even cosmologists worry about discrepancies that large!
No clue who this Tyson guy is but either he, or you, have confused Dark Energy with Dark Matter.
Then you should spend 20 seconds on Wikipedia before making an idiot of yourself in public by not knowing who one of the most famous astrophyscists in the world is. Here's a clue - watch the series Cosmos: A Spacetime Odyssey. He certainly isn't confused about the difference between dark matter and dark energy and I'm pretty certain I'm not confused either.
Physics is not determined by majority vote...
I don't recall anyone claiming that it was.
...but I very strongly suspect that the numbers will come down massively in favour of Dark Matter being an exotic form of matter by which I mean some as yet undiscovered particle.
Based on what evidence? You might be right and it may very well be exotic matter but like you said it isn't a vote. Show me any credible evidence that favors exotic matter over a flaw in the model or vice-versa. Science works on proof so go get some. Until then I remain skeptical.